Energy converter

ABSTRACT

The invention relates to an energy converter in which electrical energy output is extracted from elements exhibiting a capacitance change in response to input energy. More particularly, the invention is directed to an energy converter in which the material between the capacitor electrodes is modified by physical movement of the material between the capacitor electrodes to modify the capacitance.

{1 R 3 a 6 l U s 9 7 0 Inventor Selby M. Skinner Baltimore, Md. Appl.No. 654,243 Filed July 18, 1967 Patented Oct. 5, 1971 AssigneeWestinghouse Electric Corporation Pittsburgh, Pa.

ENERGY CONVERTER 3 Claims, 14 Drawing Figs.

US. Cl 310/10, 310/5 int. Cl H02k Field of Search 310/2, 4, 5, 10, 11;320/1; 307/1 10, 108, 9; 73/516 LM, 516; 322/2.1

HEAT SOURCE [56 References Cited 0 n UNITED STATES PATENTS 2,413,39112/1946 Usselman 307/108 X 3,008,334 11/1961 Lees 73/503 3,154,69910/1964 Courtney-Pratt 307/108 2,449,077 9/1948 Lindenblad 307/1082,628,330 2/1953 Williams 315/200 Primary Examiner-David X. SlineyAttorneys-F. l-l. Henson, C. F. Renz and R. L. Gable PATENTEDUEI 5|97|3,610,970

' SHEET 2 OF 3 FIG. 3A

+++++++ 42 FIG. 3B

FIG. 3C

FIG. 30

FIG. 3E

WITNESSES INVENTOR 19AM Q M Selby M.Skinn2r g BY BACKGROUND OF THEINVENTION This invention is related to energy conversion and moreparticularly to those devices in which an input energy in the form ofthermal or other forms of energy are converted into an electrical energyoutput. One particular application of'this invention is to provide anefficient lightweight electrical energy source particularly I for spacevehicles and their associated equipment.

Even in the best of solar cells, only a small fraction of the incidentenergy is converted into electricity. The remainder exists as heatenergy and must be dissipated or converted by other means. Nucleardevices, engines, rocket exhausts, magnetohydrodynamic, thermionic andother means of energy conversion yield a sizable amount of unconvertedthermal energy.

It is accordingly an object of this invention to provide means to changeavailable energy to electrical energy.

It is still another object to provide from radiations normally availableto space vehicles an efficient kind of lightweight device to provideelectrical energy and particularly from the heat produced by theradiations.

One method of energy conversion which heretofore has been investigatedonly slightly for energy conversion utilizes the change of capacitanceof an electrical capacitor. It is found that if a capacitor is chargedand then its capacitance is changed, the difference in electrical energycontent is:

r z) depending upon whether the change in capacitance is performed atconstant charge or at a constant voltage. The electrical energy obtainedby decreasing the capacitance of the charged capacitor must haveoriginally been furnished by the phenomenon which causes the change inthe capacitance.

One method of changing capacitance ismodifying the dielectric constantof the material between the electrodes. One method previously studied isthe thermodielectric cycle in which a temperature change in thedielectric results in a change in the dielectric constant. The resultsof the study of devices based on this thermodielectric cycle indicatedthat these devices would not be competitive with solar cells. Difficultywas found in finding materials which had sufficiently large values ofchange in dielectric with change in temperature over a sufficienttemperature range. It was also difficult to obtain rapid enough heatingand cooling of the thermodielectric materials to permit efficientcycling at rates of more than 1 hertz. The structure did have theadvantage that heat which cannot be utilized by solar cells can beconverted by the thermodielectric cycle.

SUMMARY OF THE INVENTION This invention provides an energy conversionsystem in which a first material within the region between theelectrodes of a condenser is replaced by a second material having alower dielectric constant than the first material after the capacitorhas been charged. The cycle consists of charging the capacitor,replacing the first material by a second material of lower permittivitythan the first material, discharging the capacitor and restoring thefirst material. If a condenser is charged and then the material replacedby one of lower dielectric constant, the capacitance of the condenser isdecreased and its electrical energy increases. The electrical energyoutput of the condenser results from the input energy to replace thematerial between the electrodes. The necessary mechanical force formoving the dielectric can arise from a thermal input, mechanical input,electrical input or magnetic input. The necessary requirement is thatthe input energy exerts the necessary force to move the materials.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic showing of anenergy conversionsystem for converting thermal energy to electricalenergy and embodying the teaching of this invention;

FIG. 2 is a cycle diagram illustrating the operation of the device inFIG. 1;

FIG. 3 is a diagrammatic view also for explaining the operation of thedevice illustrated in FIG. 1;

FIG. 4 illustrates another energy conversion system incorporating theteachings of this invention illustrating a mechanical energy input and adual capacitor system; and

FIG. 5 is a diagrammatic view illustrating the operation of the deviceshown in FIG. 4.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. 1, there isillustrated an energy conversion system for converting thermal energyinto electrical energy. A condenser unit l0 provides an enclosureincluding two separated top and bottom plate members 12 and 14 ofsuitable electrically conductive materials such as solid metals such ascopper, silver or aluminum; liquid or solid metal films on suitableinsulating dielectric coatings such as evaporated aluminum, copper orsilver and including what is usually referred to as metallized plastics,conducting alloys and heavily doped semiconducting materials. To avoidleakage or dielectric breakdown, it is desirable but not necessary toprovide dielectric coating 16 and 18 of a suitable material such asmylar of a thickness of about 1 mil or less on the inner surface of thetwo electrodes 12 and 14 respectively. Other suitable materials arepolyethylene terephthalate, H-film (polyimide) and FE? fluorocarbon. TheH-film and F E? fluorocarbon are also hightemperature polymers. Sidewallmembers 20 extending from the electrodes 12 and 14 complete theenclosure. The sidewall members 20 should'be of a high-resistancematerial such as a plastic. Openings22 and 24 are provided in oppositesidewalls 20 and a conduit 26 extends from the opening 24 to adielectric storage chamber 28. A conduit 30 is provided from the otheropening 22 through a suitable smoothing or valve chamber 32 to a thermalreservoir 34. The conduits 26 and 30 should be of high-resistancematerial, such as a plastic, adjacent the condenser 10 to not affect itsoperation. The remaining portions of conduits 26 and 30 can be made ofmetallic materials such as copper.

The reservoir 34 is simply an enclosure of a suitable material such ascopper and having a large planar heat absorbing surface 36 onto whichthe heat radiations from a source 38 are directed. The heat absorbingsurface should be large in comparison to volume of the reservoir 34. Thesurface 36 may be treated to increase the absorptivity. The reservoir 34contains a suitable liquid dielectric material such as methanol referredto hereafter as a replacement dielectric material 40. This replacementdielectric material 40 is of low dielectric constant and fills thevolume including the conduit 30, the chamber 32, the reservoir 34 andthe enclosure within the condenser 10 to a movable diaphragm 31 therein.The replacement material 40 may be a solid liquid or gas. Solid nonpolarpolymers such as polyethylene, polimide, mylar and FE? fluorocarbon aresuitable. Methanol or ethanol may provide. a suitable liquid. Nitrogenmay serve as a suitable gas. At a predetermined temperature thereplacement dielectric material 40 will be removed from the enclosuredefined by the condenser 10 and the condenser 10 will be filled with anoriginal dielectric material 42 of a high-dielectric constant materialsuch as water, formamide, hydrozine or methanol. The original material42 may be a solid or a liquid. The original material 42 has a higherdielectric constant than the replacement material 40. Upon applicationof heat to the reservoir 34 the replacement dielectric material 40expands and forces the dielectric material 42 from the condenser 10through the conduit 26 and into the dielectric storage chamber 28. Thediaphragm 31 operates to keep the materials 40 and 42 separated.

A suitable electrical circuit is illustrated in FIG. 1 for extractingelectrical energy as a result of capacitance change. The upperconductive electrode 12 may be connected to ground and the lowerelectrode 14 may be connected by lead 46, to a suitable switchingcircuitry. The operating condenser 10 is connected to a first diode 48and .a second diode 50. The

lead 46 is connected to the anode of the diode 50 and the cathode of thediode 48. A suitable diode for the elements 48 and S is a low-leakagediode such as a Fairchild FD 300 diode, or any high-voltage diode stackwith less than -1 A. reverse current, or one or more double-anode Zenerdiodes with similarly low-leakage current. The anode of the diode 48 isconnected through a switch 52 to a terminal 56 of an inductance 58. Thecathode of the diode 50 is connected through a switch 54 to the terminal56 of the inductance 58. The other terminal 60 of the inductance 58 isconnected to one electrode of a charging capacitor 62 with the otherelectrode of the capacitor 62 connected to ground. The terminal 60 isalso connected to a first terminal of a double anode Zener diode 64. Thelead 46 is also connected through a switch 74 to the cathode of a diode70 with the anode of the diode 70 connected to a terminal 86 of aninductance 88. The lead 46 is also connected through a switch 72 to theanode of a diode 78. The cathode of the diode 78 is connected to theterminal 86 of the inductance 88. The other terminal 90 of theinductance 88 is connected through a load capacitor 92 to ground. Theterminal 90 is also connected to the second terminal of the double anodeZener diode 64.

The operation of the system may be described by reference to FIGS. 1, 2and 3. If it is first assumed that heat is prevented from radiating ontothe thermal reservoir 34, the original material 42 will substantiallyfill the enclosure in the condenser 10 as illustrated in FIG. 3A. Thesequential heating and cooling of the reservoir can be accomplished inany suitable manner. For example a shutter might be utilized or thereservoir might be rotated as in a space vehicle. The switch 52 isclosed which permits the charging condenser 62 to send charge throughthe inductance 58 and the diode 48 to the condenser 10. Charge is placedon the condenser 10 and the inductance 58 and the diode 48 causes thecurrent flow to continue to reversal and stop, thus transferring amaximum amount of energy to the condenser 10. The switch 52 is thenopened. This charging operation is also illustrated in the diagram inFIG. 2 wherein the arrow indicates that the step of charging thecondenser 10 is accomplished during the period on the cycle from one totwo. The charged condition is illustrated in FIG. 33.

After the charging of the condenser 10, the heat is directed onto thereservoir 34 causing the replacement material 40 to expand and displacethe original material 42 driving the original material 42 into thereservoir or storage chamber 28 and forcing the replacement material 40into the condenser 10. This is illustrated in the cycle between 2 and 3of FIG. 2 and also FIG. 3C.

The switch 72 is closed which permits the condenser 10 to dischargethrough the switch 72, the diode 78 and the inductance 88 to the storagecondenser 92. Because of the higher voltage on condenser 10, the chargeand energy flow into the load condenser 92. Again the inductance 88 andthe diode 78 eliminate the energy loss when contact is made between thetwo condensers with unequal energy. The discharge of the condenser 10 isillustrated by FIG. 3D and also between the points 3 and 4 on the cyclein FIG. 2. The heat directed onto the reservoir 34 may then be removedand the cooling permits the replacement material 40 to return to itsoriginal volume permitting the original material 42 to till thecondenser 10 and the cycle is ready to repeat. This restoring of theoriginal dielectric is indicated by the diagram in FIG. 3B and betweenthe points 4 and I in the cycle diagram .ofFIG. 2.

As previously explained the capacitance of a condenser 10 can be changedby changing the materials between the electrodes I, 12 and 14. If thecondenser 10 is charged with the original material of high dielectricconstant, and the replacement material 40 of lower dielectric constantis then inserted to decrease the capacitance without changing the chargeon the condenser, the voltage across the condenser increases. Here, thisincrease of energy is: r)(Q )[l/C l/C,]. C,is the original capacitanceand C is the capacitance with a material of less dielectric constant.The electrical energy obtained must be furnished by the phenomenon orphenomena which cause the dielectric of condenser 10 to change. Thechange of the dielectric within a condenser may be provided asillustrated in FIG. I by utilizing thermal expansion of solid, liquid orgas or the expansion during a phase change or a chemical change to pushone dielectric out of the region between the electrodes of the condenserand substitute another material. For the purposes of this invention, thegeneral term dielectric includes conductors. The distinguishing featureof the conductor being that it represents a dielectric of infinitedielectric constant. If the condenser is charged and then the materialreplaced by one of a lower dielectric constant, the capacitance of thecondenser is decreased and its electrical energy increased. Thedifference in electrical energy is obtained at the expense of heat orother energy which causes the expansion of a material which accomplishedthe change in the dielectric in the condenser.

By discharging the condenser when the replacement material is in place,the additional energy is extracted from the system. If then thereplacement material is cooled so as to cause contraction and bringabout return of the original material in the condenser, the condensercapacitance reverts to its original value so that charging once againcan be performed and a new cycle commenced. Periodic charging, change ofmaterial, discharging, and return of the original material is arepetitive cycle in which heat energy disappears and electrical energyappears.

In the specific embodiments shown in FIGS. 1 and 3, a planar geometrytype of condenser is illustrated. It is also possible to utilize aconcentric capacitor member and utilize the inner electrode as oneconductor and the outer conductor as the other electrode. It is evidentthat the capacitance and therefore the energy changes obtainable withthis replacement dielectric cycle are much larger than can be obtainedon change of dielectric constants of single dielectric or ferroelectricmaterials as used in the thermodielectric method of ener gy conversion.The increased energy in the condenser is obtained at the expense of thework required to remove the original dielectric or conducting fluid fromthe condenser and replace it by the replacement material of a lowerdielectric constant. This work is a direct result of the expansion ofafluid in a central reservoir which is subjected to the radiation orother heating and in the other half of the cycle to the radiativecooling. It is also obvious that the cycle can be performed in reversethat is, the conductor or higher dielectric material is brought into thespace between the electrodes upon the heating of the reservoir and isremoved through suitable means, and replaced by lower dielectricconstant material during cooling. This merely requires obvious changesin the electrical cycling.

Instead of relying upon internal cohesion of the fluid duringcontraction to produce the reverse flow during cooling, a reversepressure may be used to provide a positive flow of the originaldielectric back into the reservoir. This reverse pressure may beexternal or may be automatic as in a gas which is compressed by themovement of a dielectric during expansion and pushes back during thesubsequent cooling. In the latter case, it will oppose the flow of thereplacement material in the condenser during the heating cycle and thework done on it will be recovered during the cooling cycle.

Suitable materials for the fluid particularly a conductor would beliquid metal such as mercury, gallium, cesium or rubidium in appropriatetemperature ranges. Other suitable materials would be fused salts orconducting solutions such as electrolytic materials. For space use, thelow density of cesium and rubidium would be advantageous if corrosionand degradation problems could be overcome. Plastic film materials orwaxes are suitable for films covering the electrodes. lf conductingfluids are not used but high-dielectric constant fluids are usedinstead, any suitable noncorrosive organic or inorganic material whichhas a high dielectric constant and is liquid at the temperature ofoperation and meets other requirements may be used. Since the conversionof energy is accomplished by forcing a dielectric out of the condenser,other types of energy can be used to accomplish the same effect. Thus ifthe energy conversion is designed so that external pressure acts on thefluid in the reservoir then the energy of winds, waves, tides or othersources can be utilized. This system is also adapted to nuclear sourcesof power to utilize the direct or waste heat therefrom.

Referring to FIGSA and 5 there is illustrated a dual capacitor orpush-pull type system. In FIG. 4 there is illustrated an engine 100which may be of wind, tidal or other power provided with mechanicallinkage for driving a piston 102 within a closed system 104. The closedsystem 104 includes a first capacitor 106 and a second capacitor 108.The piston 102 is within a cylinder 109 with conduits 111 and 113connecting the cylinder 109 to the condensers 106 and 108 respectively.Valves 115 may be provided in conduits 111 and 113 for control;diaphragms 117 may be provided for isolating the material 110 from 112.A material 1 with high dielectric constant such as described above fillsthe capacitor 106 and the rest of the system 104 is filled with amaterial 112 of low dielectric constant such as described above. By amovement of the piston 102 the type of material within each condenser106 and 108 may be changed from either material 110 or 112 to the other.By using two capacitors, a material may be pushed from a first condenserinto a second condenser instead of into a storage chamber and in thesecond half of the cycle the material can return to the first condenser.By charging each capacitor while filled with a material having a highdielectric constant and then replacing with a material having a lowdielectric constant each capacitor performs a cycle. This is illustratedin FIG. 5. Again the dielectric may be a solid, fluid or gas. Since workis being done on each half of the cycle, force is required to push thedielectric in either direction in either half of the cycle. A completecycle provides the charging of the capacitor 106 when thehigh-dielectric constant material 110 is between the plates andsimultaneously capacitor 108 is being discharged with material 112between the plates since it is in a high energy state. This isillustrated in FIGS. 5A and 5B. The high-dielectric constant material 110 is then pushed from the charged capacitor 106 into the unchargedcapacitor 108 and piston 102 is positioned as shown. The work inputincreases the energy in capacitor 106 and there is no change in theenergy in capacitor 108. This is illustrated in FIG. 5C. The high energyon capacitor 106 is now removed by removing the charge and letting itflow into the storage output capacitor. Simultaneously a charge isplaced on capacitor 108 as is illustrated in FIG. 5D. The piston 102 isthen moved in opposite direction and will displace the high dielectricmaterial 110 from capacitor 108 into capacitor 106. The energy incapacitor 108 increases but there is no change in the energy ofcapacitor 106 which is uncharged. This is illustrated in FIG. 5E andcompares to 5A. Capacitor 108 is now discharged electrically thusextracting its energy and simultaneously capacitor 106 is charged; asillustrated in FIG. 5F and compares to FIG. 5B. The system is now in theoriginal condition and the cycle has repeated itself.

The two-capacitor cycle illustrated in FIGS. 4 and 5 may be regarded asa subdivision of the capacitor 10 shown in FIG. 1.

The capacitors may be stepped successively in the cycle of operation.The output voltage will be n times that obtainable with a singlecapacitor.

Solid dielectric structures may be utilized. A piston or rotation of acylinder provides means of positioning alternately high and lowdielectric materials between plates of a con denser. The charging anddischarging of the capacitor is correlated in time with the changeofdielectric so that the same type of cycling takes place as describedabove with regard to fluid dielectrics.

Although the present invention has been described with a certain degreeof particularity, it should be understood that the present disclosurehas been made only byway of example and that numerous changes in thecombination and arrangement of elements and components can be resortedto without departing from the scope and spirit of the present invention.

Iclaim:

1. An energy conversion system comprising a condenser member having afirst and second electrode members, a first means of a predetermineddielectric constant, a second means of a dielectric constant differentfrom said predetermined dielectric constant, means for sequentiallypositioning said first and second means within a space between saidfirst and second electrodes, said means for sequentially positioningsaid first and second means comprising a reservoir having a charge-areaheat-absorbing surface and in which said first means is a liquidmaterial and fills said reservoir, said liquid material exhibiting theproperty of expansion of volume in response to heat.

2. An energy conversion system comprising a condenser member having afirst and second electrode members, a first means of a predetermineddielectric constant, a second means of a dielectric constant differentthan said predetermined dielectric constant, means for sequentiallypositioning said first and second means within a space between saidfirst and second electrodes, first circuit means including switchingmeans and inductance means coupled to said condenser to store electricalcharge when said first means is within said space, second circuit meansincluding switching means and inductance means to extract said chargewhen said second means is within said space, said first and second meanscomprising liquid separated by a diaphragm in said system and saidpositioning means comprising a piston movable in response to inputenergy to thereby position said first and second means.

3. An energy conversion system comprising a first condenser memberhaving a first and second electrode members, a first means of apredetermined dielectric constant, a second means of a dielectricconstant different than said predetermined dielectric constant, meansfor sequentially positioning said first and second means within a spacebetween said first and second electrodes, first circuit means includingswitching means and inductance means coupled to said condenser to storeelectrical charge when said first means is within said space and secondcircuit means including switching means and inductance means to extractsaid charge when said second means is within said space, a secondcondenser, said first and second means alternating between saidcondensers and in which said first and second circuit means alternate instoring and extracting charge from said condensers.

1. An energy conversion system comprising a condenser member having afirst and second electrode members, a first means of a predetermineddielectric constant, a second means of a dielectric constant differentfrom said predetermined dielectric constant, means for sequentiallypositioning said first and second means within a space between saidfirst and second electrodes, said means for sequentially positioningsaid first and second means comprising a reservoir having a charge-areaheat-absorbing surface and in which said first means is a liquidmaterial and fills said reservoir, said liquid material exhibiting theproperty of expansion of volume in response to heat.
 2. An energyconversion system comprising a condenser member having a first andsecond electrode members, a first means of a predetermined dielectricconstant, a second means of a dielectric constant different than saidpredetermined dielectric constant, means for sequentially positioningsaid first and second means within a space between said first and secondelectrodes, first circuit means including switching means and inductancemeans coupled to said condenser to store electrical charge when saidfirst means is within said space, second circuit means includingswitching means and inductance means to extract said charge when saidsecond means is within said space, said first and second meanscomprising liquid separated by a diaphragm in said system and saidpositioning means comprising a piston movable in response to inputenergy to thereby position said first and second means.
 3. An energyconversion system comprising a first condenser member having a first andseCond electrode members, a first means of a predetermined dielectricconstant, a second means of a dielectric constant different than saidpredetermined dielectric constant, means for sequentially positioningsaid first and second means within a space between said first and secondelectrodes, first circuit means including switching means and inductancemeans coupled to said condenser to store electrical charge when saidfirst means is within said space and second circuit means includingswitching means and inductance means to extract said charge when saidsecond means is within said space, a second condenser, said first andsecond means alternating between said condensers and in which said firstand second circuit means alternate in storing and extracting charge fromsaid condensers.